The present invention relates to a demand-assignment communication system, and more particularly to a satellite communication channel assignment system therefor.
In an FDMA (Frequency Division Multiple Access) satellite communication system which accomodates a number of earth stations and handles plural kinds of communication circuits with different transmission frequency bands corresponding, respectively, to a plurality of transmission rates,a demand-assignment communication system has been employed, in which a plurality of earth stations share a plurality of satellite communication channels and in-which, upon each occurrence of a call, one of the satellite communication channels corresponding to the transmission frequency band necessary for the call between a calling earth station and a called earth station is assigned, so that the utilization efficiency of the satellite communication system increases in comparison with a system in which communication circuits corresponding respectively to transmission frequency bands are fixedly assigned, for each kind, in the number commensurate with the traffic between earth stations.
In the above-mentioned demand-assignment communication system which assigns a satellite communication channel of the required transmission frequency band in response to the occurrence of a call, the assignment of satellite communication channels onto a common satellite transponder frequency band encounters what is called a separation fraction circuit effect which makes it impossible to assign an idle frequency band to a new call according to the state of connection of satellite communication channels since idle frequency bands are discretely separated although the sum of idle frequency bands is larger than the frequency band necessary for the assignment of the satellite communication channel to the new call.